during the hot summer of 1968, when the water temperature was 9-10°C 



higher than usual for a period of 3 weeks (Ankar, Jansson, 1973). There 



are other examples of the influence of thermal pollution on the 

 distribution of the benthos. 



Plankton . --Data on the influence of thermal pollution on the 

 distribution and composition of plankton are as yet sparse. For 

 example, it has been shown that in the vicinity of Southhampton (Pannel 

 et al., 1962; Raymont, 1964; Raymont, Carrie, 1964), thermal pollution 

 has caused a gradual increase in the population of the warm-water 

 copepod Acartia tonsa , and in the summer plankton the larvae of the 

 warm-water cirripedian El mini us modestus have become numerically 

 dominant, quite unusual for northern European waters. On the other 

 hand, in the Patuxent River estuary, the thermal discharge did not cause 

 changes in seasonal parameters of the distribution of Acartia tons a and 

 Eurytemoraaf finis (Heinle, 1969b). Similarly, off the coast of Japan, 

 the thermal discharge of nuclear power plants in most cases did not 

 result in a decrease in the population of zooplankton, and in many cases 

 there was even an increase in its population (Niva, 1973). 



Fish . — Depending on the thermopathy, various species of fish are 

 attracted to or repelled by regions of thermal discharge. In western 

 European waters, for example, cases of winter concentration of a number 

 of fish in regions of thermal discharge have been observed. 



3 . 4 Passage of Pelagic Fish through the Pipes of Water Cooling 

 Systems of Nuclear Power plants and Industrial Enterprises 



One very important form of thermal pollution is its effect on 

 pelagic animals as they pass through the pipes of the cooling systems of 

 power plants and industrial enterprises. Passage through the pipes has 

 different effects on different organisms, and this phenomenon itself may 

 lead to different ecologic results. In the Patuxent River estuary, 

 passage of phytoplankton through the pipes of the cooling system of the 

 power plant in the summer inhibits photosynthesis, while in the winter 

 it cancels the stimulating effect of the increased temperature of the 

 water on photosynthesis; as a result, it may lead to a decrease in the 

 photosynthetic activity of the phytoplankton by a factor of 10 (Morgan, 

 1969). Inhibition or stimulation of the photosynthesis of phytoplankton 

 as it passes through the cooling pipes of electric power plants have 

 also been observed in the York River estuary in Virginia (Warinner, 

 Brehmer, 1966). 



Many planktonic copepods die, primarily as a result of mechanical 

 damage, as they pass through the cooling system of the power plant in 

 the Patuxent River estuary, and 90% of zooplankton eggs lose their 

 capacity to hatch (Heinle, 1969a); in the water cooling pipes of a power 

 plant near New York, from 70 to almost 100% of the copepods died 

 (Suchanek, Grossman, 1971; Carpenter et al . , 1974). 



It has been shown for Acartia tonsa (Reeve, Cosper, 1970) that if 

 it is held at temperatures characteristic of the thermal discharge 

 waters dumped into Biscayne Bay, the mortality rate is twice as high in 

 winter as in sunmer. However, the larvae of bivalve mollusks can pass 



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